On-load tap changers (in abbreviation OLTC) are widely known and customary in the prior art. They serve for uninterrupted switching-over between different winding taps of tapped transformers. On-load tap changers are divided into load selectors and load changeover switches with selectors.
In the case of a load changeover switch with a selector such as disclosed in, for example, German Patent Specification DE 100 55 406 C1 the selector, consisting of a fine selector and possibly a preselector, is below the load changeover switch. The selector serves for power-free selection of the respective new winding tap of the tapped transformer that is to be switched over to. The load changeover switch serves for the subsequent rapid and uninterrupted switching over from the connected winding tap to the new, preselected winding tap to be connected.
Chinese Utility Model specification CN 2870107 Y discloses a control drive for an on-load tap changer comprising a transmission with a horizontal drive shaft. One end of the drive shaft can be coupled with a drive motor. The rest of the transmission is surrounded by a transmission housing. The horizontal drive shaft transmits its rotational movement to the drive input shaft by an angle gear consisting of a bevel pinion of the drive shaft and of a bevel gear of the drive input shaft.
Chinese Patent Application CN 102623210 A discloses a motor-driven transmission with a planetary gear and a setting indicator for an on-load tap changer.
Chinese Utility Model specification CN 202258744 U relates to a transmission and a transmission control for on-load tap changers, particularly with an electrical system for emergency operation. A vertically mounted drive output shaft and a drive shaft are provided in a transmission housing. The drive shaft is provided with a cross member and an axial bearing. In addition, a worm wheel on the drive output shaft is connected with the drive shaft by a worm shaft. The electrical system and the transmission control allow switching over between electrical and manual operation of the on-load tap changer.
Bulgarian Patent Specification BG 66062 B1 discloses a transmission for electric-motor actuation of an on-load tap changer. The connection of the shaft of the electric motor and the drive shaft of the on-load tap changer is realized by a planetary gear integrated in the flange of the electric motor. A control shaft is mechanically coupled with the drive shaft by a worm gear. One end of the control shaft is led out of the transmission housing and carries a disk with one or more cut-outs co-operating with a controller.
German published specification DE 35 41 888 A1 discloses a transmission for stepped actuation of a tap changer for tapped transformers with a manual drive shaft actuatable by a hand crank. A drive output shaft can be coupled with a tap changer shaft and executes one revolution per switching step. A housing comprises a speed-change transmission that couples the manual drive shaft and drive output shaft, and a switch setting indicator with a viewing window. Manual drive shaft and drive output shaft are in parallel and are mechanically coupled by an orthogonal transmission shaft via a respective worm thread. Through different gradients of these two threads the transmission can translate one revolution of the drive shaft into eight-and-a-half revolutions at the hand crankshaft, which a user has to produce in manual operation.